An estimated 178,700 women were diagnosed with breast cancer in 1998, more than half of whom were 65 years of age or older. This proportion is likely to grow, not only because older age is the most important risk factor for breast cancer, but because gains in life expectancy and decreases in deaths due to cardiovascular disease will result in more women at risk for longer periods of time. Older women are at risk for receiving less than definitive care for their breast cancer and emerging evidence suggests that this translates into poorer health outcomes. We are studying 900 breast cancer patients at least 65 years of age who are at intermediate or high risk of breast cancer recurrence to identify physician and patient predictors of tamoxifen prescription and one year treatment adherence. We propose to follow this cohort, enrolled at four different geographic sites (Los Angeles, Minnesota, Rhode Island, and North Carolina) for five years to answer critical questions about the relationships between breast cancer treatments and disease-specific and health-related quality of life outcomes. Specifically, we propose to: (l) compare the effectiveness of adjuvant tamoxifen therapy, versus no adjuvant tamoxifen therapy, in reducing breast cancer recurrence and breast cancer mortality rates among older women receiving recommended definitive primary tumor therapies and those not receiving such therapies; (2) quantify the prevalence of tamoxifen discontinuance and identify patient and physician characteristics associated with it during the recommended five years of therapy; and (3) identify risk factors associated with a decline in health-related quality of life outcomes, particularly upper body function, during five years after breast cancer diagnosis. In the parent project, patients are interviewed 3, 6, and 15 months after their definitive surgery; medical record abstractions are performed; and breast cancer physicians provide information about treatments recommended. In the proposed project we will interview the same patients at months 27, 39, and 51 after their definitive surgery; obtain additional physician recommendation information at 30 months; and obtain semi-annual medical record-documented breast cancer recurrence information as well as National Death Index cause-specific mortality information. Findings from this study will characterize the effectiveness of adjuvant tamoxifen therapy in reducing rates of breast cancer recurrence and breast cancer-specific mortality among older women at high risk for recurrence who are cared for in community practice settings. The findings will also allow us to identify women most likely to discontinue tamoxifen therapy and those most likely to experience a significant decline in health-related quality of life during the first five years following the diagnosis of breast cancer.